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Journal of Veterinary Diagnostic Investigation Vol. 21 Issue 4, 478-486
Copyright © 2009 by the American Association of Veterinary Laboratory Diagnosticians
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Full Scientific Reports

Axonal degeneration in sheep caused by the ingestion of Halimium brasiliense

Franklin Riet-Correa1, Severo S. Barros, Maria C. Méndez, Cristina Gevehr-Fernandes, Otaviano A. Pereira Neto, Marcio P. Soares and M. Donald McGavin

Correspondence: 1Corresponding Author: Franklin Riet-Correa, Hospital Veterinário, CSTR, Universidade Federal de Campina Grande, Paraíba, 58700-000, Brazil. franklin.riet{at}pq.cnpq.br

Nervous system disease is reported in sheep from 2 farms in southern Brazil and in 33 farms in Uruguay. The illness was seasonal, occurring from May to November, during the growing season of Halimium brasiliense, and primarily affected sheep older than 3 years of age. Clinical signs included transient seizures that occurred mainly when sheep were disturbed or frightened. Most affected sheep recovered when removed to other pastures. Feeding trials produced clinical signs in 1 sheep after the ingestion of 2,117 g/kg of body weight of H. brasiliense over 142 days. Two sheep that had previously recovered from spontaneous toxicosis developed clinical signs after the ingestion of 263 g and 565 g of H. brasiliense per kg body weight given over 36 and 31 days, respectively. The main histologic lesion was vacuolation of the brain and spinal cord, with rare axonal spheroid formation. Transmission electron microscopy revealed segmental axonal swelling with degeneration and disappearance of the axonal organelles and vacuolation of the axoplasm. A pigment identified as ceroid was also present in neurons, astrocytes, and macrophages. These lesions suggested a novel morphologic manifestation of a toxic axonopathy.

Key Words: Axonal degeneration • convulsion • Halimium brasiliense • seizures • sheep • toxic plants






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